The invention relates to a solderable electrical connection element having the characteristics of the preamble of Claim 1, that is, a solderable electrical connection element, comprising a thin support sheet and at least one metal conductor having at least one contact face which is provided with a solder deposit and which can be joined by soldering this solder deposit to a connection face of another component with which it is associated, characterized in that an insertion piece provided with the solder deposit and passing through the connection element is securely joined to the support sheet in the region of the contact face.
Document DE-C1-195 36 131 discloses a solderable connection element for antenna panes, in which several free contact faces and the associated conducting tracks, which are insulated from one another, are joined to a heat-resistant non-conducting support sheet, an upper sheet layer extending over the contact faces and the soldering points, respectively. The ends of conductors and the free contact faces, respectively, to be soldered are provided with solder deposits soldered to their lower or connection side. These solder deposits are remelted by supplying heat at the place where the actual welded joint is produced and they are durably joined to an associated connection face by pressing them onto the latter. Not provided here is a separating piece intended to ensure a reproducible thickness of the solder layer. At the present time, a system based, at great expense, on delivering a finely metered quantity of solder and on precisely tailored soldering tools and methods, is used so that, during pressing after melting, the soldered joint is formed with a sufficiently uniform thickness and surface distribution.
During the soldering of such connection elements in industrial mass production, only a few seconds are available for each soldering operation, during which the necessary heat must be transmitted through the support sheet to the pretinned contact faces. To optimize heat transfer in the presence of strong temperature attenuation, it is necessary to ensure that the heat supply is as extensive as possible by means of special tools. Likewise, the temperature of the tool must be well above the melting point of the solder. It is again for this reason that the support sheet must be made of a heat-resistant material (usually, polyimide or Kapton), which are very expensive materials compared with other plastics, although its heat resistance is only actually necessary over a small fraction of its total surface area.
Another problem is the reliability of the contact, which can only be checked at great expense, after making the soldered joint, for example by X-ray examination.
In the prior art, the contact zone is provided, on its side facing the corresponding connection area on the pane, with at least one narrow adhesive tape, which extends in a straight line as far as the conducting tracks with a relatively small width. Thus, the connection element may be positioned and temporarily fastened to the window pane. Moreover, the adhesive tape serves to relieve the tensile force in the actual contact zone; if necessary, the tape can also go completely around the contact zone in a ring and thus very extensively protect it from environmental effects (moisture, soiling).
Document DE-C2-43 04 788 discloses a prefabricated laminated component consisting of a thin metal strip and of an insulating sheath, composed of thin layers of plastic sheets, which surrounds the strip. This connection element, also called a flat conductor is provided locally with coaxial holes in the two layers of the insulating sheath and of the metal layer, which holes form a contact window. Into the latter may be introduced molten solder, by means of which the metal strip is securely connected to an electrical conductor installed, for example, on a pane. This construction of a contact window also allows, by serving as an observation window, simple visual inspection of the soldering point. This connection element may also be adhesively bonded to the surface of the pane.
Finally, it is known to provide crimp connectors on such flat conductors, for example, on the one hand, to securely fasten an end plug or electrical switching elements to the conducting tracks and, on the other hand, to electrically connect it (them) to these conducting tracks with a sufficient cross section. A metal insertion piece, with a cross section substantially in the form of a U and with branches at the toothed free ends, is placed on the sheet. The teeth are pressed or forced by means of a suitable manual or mechanical tool through the sheet and, in the manner of a knife contact, through the conducting track and are then turned up laterally, thus producing a joint which is formed by mechanical interlocking and is, furthermore, electrically conducting. In general, incorporated into the abovementioned plastically deformable U-shaped region are contact tabs or bars, or other soldering faces.
It is an object of the invention to provide another solution for forming solder deposits on solderable electrical connection elements of the type mentioned in the introduction.
In accordance with the invention, this objective is achieved by the characteristics of Claim 1: that is, a solderable electrical connection element, comprising a thin support sheet and at least one metal conductor having at least one contact face which is provided with a solder deposit and which can be joined by soldering this solder deposit to a connection face of another component with which it is associated, characterized in that an insertion piece provided with the solder deposit and passing through the connection element is securely joined to the support sheet in the region of the contact face. The characteristics of the secondary claims provide advantageous improvements of this object. Claim 11 presents, by way of preferred use of at least one connection element according to the invention, that for a window pane, with improvements described in secondary claims 12 and 13.
If the region of the contact point to be furnished with a solder deposit is provided with a metal insertion piece, securely joined to the support sheet and passing through it, this piece thus forms in several regards a better base for the formation of the solder deposit. For example, it is no longer necessary to heat the connection element itself, or alternatively its support sheet, whether the solder deposit is formed, according to a first variant, by soldering a quantity of solder to the insertion piece or whether, according to a second variant, it is fastened only by mechanical interlocking to the support sheet at the same time as the insertion piece.
Particularly preferably, it is necessary to provide a direct contact, or alternatively a direct connection, of the solder deposit with the contact face of the connection element so as to prevent the occurrence of multiple transition resistances. It is not necessarily essential to bring the metal of the insertion piece directly into contact with the conducting track or with the stripped end of the cable. The contact face is soldered directly to the corresponding connection face of the component to be electrically contacted, for example an antenna pane or a heating pane.
However, optionally, there is also the variant consisting in putting the insertion piece into electrical contact with the respective conductor, while the solder deposit is connected directly only to the insertion piece and later, of course, to the respective corresponding connection face. In such a case, that part of the insertion piece which is provided with the solder deposit directly forms the contact face of the respective conductor.
The electrical conductor may have the shape of a conducting track joined flat to the support sheet or embedded in the latter and/or also of a cable joined at least mechanically to the support sheet. In the latter case, the contact face is opportunely formed by removing the insulation at the end of the cable. In this way, several cables brought in individually may also, particularly advantageously, be maintained in a predetermined spatial arrangement by very simple means on the support sheet of the connection element.
It goes without saying that various configurations of electrical conductors and of their contact faces may also be combined or brought together on a single support sheet. Thus, for example, additional conductors (cables) may, where required, also be placed on a connection element which is normally equipped with a predetermined number of conducting tracks. The individual conductors will, in principle, be insulated from one another. However, it is also possible to bring, as an addition, a cable to be connected into electrical contact at the same time with an existing conducting track and with the associated corresponding connection face, if a corresponding need were to arise.
In a preferred embodiment, the insertion pieces are, before they are joined to the connection element, configured so as to have a cross section approximately in the form of a U with free ends of the toothed branches whose teeth are pressed or forced through the connection element and then turned up laterally by plastic deformation. Of course, it is also possible to imagine other shapes of insertion pieces. However, the preferred shape here promises the best results in terms of possible mechanical processing and its good cost-effectiveness.
As an additional advantage, the insertion piece allows markedly better heat supply to the solder deposit during the subsequent soldering of the contact face to the corresponding connection face. Since the insertion piece passes through the connection element, one of its sides remains free after the placing of the contact face, or the solder deposit, on the base and can be used for supplying heat to the actual soldering point.
Given that metals conduct heat much better than plastics, this results in markedly improved heat transfer from the soldering tool to the solder deposit. Where appropriate, it is possible to switch from supplying heat flat to soldering irons, to a laser and the like. The time required for the soldering operation is significantly reduced. The temperature of the tool can be lowered. Furthermore, a less heat-resistant and consequently less expensive plastic may possibly be used as the support sheet. Finally, the thermal load around the soldering points decreases.
Yet another advantage of the metal insertion piece is its spacer role. The minor drawback of a greater thickness with respect to the contact zone of the known flat-cable connection element is advantageously more than compensated for by the fact that the insertion piece, or its turned-up teeth, are kept permanently at a predetermined height above the contact face. The space created here can be filled with the solder deposit with sufficient reliability and is at the same time firmly bounded so that normal application during melting can no longer cause lateral expulsion of the solder material. Thus, an improvement in the quality of the soldered joints may also be expected. Another consequence of the increased certainty of preventing lateral expulsion of the solder is that the distances between neighbouring contact faces can be made smaller than in the prior art, because the risk of short circuits by expelled solder is considerably reduced.
Yet another advantage over forming solder deposits directly on the conducting tracks is the intrinsic mechanical rigidity of the insertion pieces. If a force is exerted on the connection element, the soldered joints produced with insertion pieces are more difficult to break than those not having insertion pieces, so that it is possible to dispense with the additional security provided by adhesive tapes or the like.
Likewise, according to an improvement and, as in the prior art, adhesively-bonded joints may also be provided in the contact zone between the connection element according to the invention and the other component, for example in order to protect the soldering point from the effect of moisture or of soiling.
Despite their slightly greater thickness in the contact zone, the connection elements according to the invention can be used not only on free surfaces of monolithic window panes, but also on window surfaces which lie within laminated panes. The adhesive films normally used in laminations are again much thicker than the contact zones and can encapsulate them without any difficulty.
The application of the connection elements described here is not, however, limited to the electrical connecting of window panes.
Overall, and whatever the envisaged use, the fitting of connection elements with the insertion pieces, coupled to the formation of the solder deposit, can be mechanized to a great extent, just like the manufacture of the actual soldered joint, using the spacer function of the insertion pieces.
Further details and advantages of the subject of the invention will become apparent from the drawing of preferred illustrative examples and from the detailed description thereof which is given below.